Oily sludge refers to the soil mixed with heavy oil such as crude oil, various refined oil products, and residual oil, the soil forms an oily sludge which is extremely difficult to be treated. The oil fields will produce a certain amount of oily sludge during the oil and gas production process, the oily sludge is mainly derived from two aspects: a first aspect resides in that the crude oil is carried from the underground stratum to the ground, and is deposited in various facilities such as containers, large tanks and recycling pools, thereby form the sludge which shall be regularly cleared; the second aspect is the landed sludge generated during the oil well operation, perforation of the oil collection and transport pipeline, and oil-stolen activities. The oily sludge is harmful to the human body, plants, water body and organisms. The oil and gas evaporated in the air may irritate the skin, eyes and respiratory organs, result in that the land loses the function of growing plants, it is difficult to treat and renovate the oily sludge. Because the physicochemical properties of the oily sludge in the oil fields are very complicated, it is extremely difficult to separate and treat the oily sludge, which is one of the main pollutants in the petroleum and petrochemical industries. The oily sludge belongs to HW08 hazardous waste according to the “List of National Hazardous Wastes”. When confronting with such a troublesome sludge, the enterprises used to deal with oily sludge with two methods, namely burying and incineration.
The burying method is to find a place and dig a pit for the oily sludge, and bury the oily sludge after conducting anti-permeation measures. Such a method will occupy a large amount of land and has a limited capacity. The incineration method is to incinerate the oily sludge at a high temperature. The method may reduce wastes and incinerate pollutants, and recover a part of heat. But the method has disadvantages that it requires to consume a large amount of fuel and the operation cost is high.
The pyrolysis treatment technology of oily sludge refers to decomposing the heavy oil in oily sludge into volatile low-carbon hydrocarbon fuel, synthetic crude oil, solid carbon and the like under the heating condition, the technology is considered as the most promising processing technology with industrialization prospect. At present, the developed pyrolysis treatment technology is mainly the oily sludge pyrolysis treatment technology based on the externally heated rotary kiln reactor, and the effects of reducing quantity and resourceful utilization are very obvious. However, the technology has the defects such as low heating rate and long reaction time, which results in that the liquid yield is low, the large treatment scale cannot be easily achieved, the pyrolysis residue contains a high content of petroleum hydrocarbons and heavy metals, thus the harmless utilization of the residue has become a bottleneck restricting the industrial popularization and application of the technology.
Therefore, high-efficiency pyrolysis of oily sludge and harmless treatment of residue which achieve harmlessness, reduced quantity and resourceful utilization of the oily sludge, it have become the focus and hotspot of current oily sludge treatment.